It has been observed that anorexia nervosa (AN) patients present osteoporosis (OP) although the mechanism by which it occurs is not well known. The reduction in calcium intake as well as a decrease in estrogen production which is associated with involutive OP, could be involved. We have found in the literature 16 cases of AN and OP, one of which presented a fracture of the sternum. We now present another case of fracture of the sternum. This implies a high incidence of this type of fracture in OP due to AN which is extremely rare in involutive OP, which suggests that the ethiopathogenic factors of the former are different from those of the latter.